1. Field of the Invention
The present invention concerns a valve device for installation in pressurized gas or air piping and which may be controlled by means of the relative pressure of the gas applied to one port of the valve device or by the pressure differential between two ports, passages or circuits thereof. According to the invention, the state of the valve device may be remote-controlled via the air pressure in the pipe connected to that port, passage or circuit, without auxiliary control lines, by varying the air pressure applied to an end of the piping. In particular, it concerns a three-state valve device adapted to operatively adopt a closed position, an open position between one pair of ports or an open position between another pair of ports, according to the pressure state in one of the ports, i.e. a valve control port, with reduced friction between the valve components and more accurate and effective operation.
The valve device of the present invention may be applied to any pressurized installation where the pressure of the installation may be desired to be controlled, such as increased, released or decreased. Such an installation may be a circuit for pumping (inflating) and unpumping (deflating) pressurized loads, in particular as a valve for a tire, such as a component for a tire-pressure control system in a motor-car vehicle. Such systems are used in transport vehicles, especially lorries and buses, since they enable corrective action to be carried out, either automatically or via driver manual control means, on the inflation state of each tire and/or wheel axle without having to stop, thereby providing an important safety feature for transport.
In the mentioned application, the valve device is inserted, for example, between one end of the piping of the installation and the air input of the tire, replacing or applying it to the conventional valve of the wheel and provides for the three fundamental operations of the system, that is: to shut off the passage of air when the installation is underpressurized, to avoid the tires of the vehicle going flat, to enable sufficient air flow to pump a tire up or keep it inflated, in case of puncture for example, to avoid the vehicle having to stop anywhere, and to enable the tires to be deflated, for example for lowering the tire pressure because of road conditions.
In this application, the control port, which is coupled to one side of a plunger of the valve device, is connected to the piping. In addition to providing the state control pressure signal, at the same time it supplies the air (gas) for inflating; while a second port, coupled to an opposite side of the, plunger, is connected to the tire tube and the third port may be arranged as a vent for airing pressure from the second port.
2. Description of the Prior Art
A valve device of the type above mentioned is disclosed in the U.S. Pat. No. 6,672,328 to the same inventors of the present application and which is referred herein in its entirety as a reference.
U.S. Pat. No. 6,672,328 discloses a pressure-controlled three-way valve device of the type having a valve body 13 housing an inlet circuit or passage 15A extending longitudinally between two air ports 17A, 17C provided at respective longitudinally-opposite ends 19 of the valve body 13. The port 17A is for the inflow of inflating air. Accordingly, it is coupled to the pressurizing installation piping (not shown), from which it receives both the inflating airflow and pressure signals for controlling the valve device 11. The port 17C is coupled to the tire tube (not shown), such that it behaves as an inflating air inlet/deflating air outlet conduit. A port 178 is provided on one side of the valve body 13 to define a deflating air outlet port in communication with port 17C through an outlet circuit 15B. The valve body also houses a plunger 21 having a longitudinal stroke and urged by a spring towards the inlet port 17A end. The valve body also including an outlet valve which is closed at respective end positions of the plunger in a manner that the valve is open when the position of said plunger is in an intermediate range.
As it is disclosed in the cited US Patent, the outlet valve comprises a pair of circumferential steps 41A, 41B, formed in the outer wall surface of the plunger in order to define a recess which is in correspondence with a stationary seal or seat that is comprised of a sealing O-ring extending inwardly from the inner wall of the valve body and having a pair of circumferential sealing lips in correspondence with the cited steps in a manner that, en both end positions of the plunger stroke, one predetermined of the moving steps of the plunger seats against the corresponding lip thus closing the outlet circuit or passage which is open, through respective gaps formed between the lips and the steps, only when the plunger is at the intermediate position. The inlet passage 15A passes through the plunger and through a valve normally-closed by a piston 27 axially slidable within the valve body 13 and urged by spring 23 against a plunger end. In operation, the plunger is a movable seat for the inlet valve and a plurality of intermediate pressures are in charge of moving the plunger between its end positions to actuate the outlet valve.
An o-ring is mounted in the plunger in order to keep a sealing contact between the outer wall surface of the plunger and the inner wall surface of the valve body to guarantee an effective operation of the valve device. This device has shown satisfactory operation in several applications, however, this O-ring employed to prevent shortcircuits between the inlet circuit and the outlet circuit imposes a friction that offers an important resistance to the movement of the plunger to open the outlet/inlet valve. It is foreseen that, due to manufacturing tolerances, composition material, origin, aging, size variations due to lubricant effects, etc., of the O-ring, the calibration of the operation of the valve device may be affected, particularly in connection to the pressure rates controlling the opening of the outlet valve as well as the influence of foreign dirty and particulate material that can enter through the venting port.
In order to improve reliability and operation speed of the valve device, the average initial friction of the O-ring is compensated by adding a second spring or equivalent elastic means to provide a threshold force urging of the plunger towards the inlet valve having a piston or closing means moveably seated on the plunger. This spring is in opposition to the first spring urging the inlet valve against the plunger and is dimensioned to yield to the force of the latter absent enough air pressure at the inlet port and, at the same time, urge the plunger to recover faster in response to a control pressure signal at the inlet port. The above reference numbers are those employed in the specification of U.S. Pat. No. 6,672,328.